Method of positioning a wafer with respect to a focal plane of an optical system
US5268744A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 4, 1991 |
| Grant date | Dec 7, 1993 |
| Priority date | — |
| Expiry date | Apr 4, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F9/7023
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A method of positioning a surface of a wafer with respect to a focal plane of an optical system is disclosed. The method includes: forming an image of a pattern in a first region of a wafer through the optical system; projecting through the optical system a radiation beam to the first region of the wafer and projecting through the optical system a reflection beam from the first region of the wafer onto a predetermined plane; evaluating the formed image to determine the focal plane of the optical system and determining, as a reference position, a position of incidence on the predetermined plane of the reflection beam from the first region of the wafer at a level corresponding to the determined focal plane; projecting a radiation beam to a second region of the wafer and projecting through the optical system a reflection beam from the second region of the wafer onto the predetermined plane; and positioning the second region of the wafer on the determined focal plane of the optical system on the basis of a position of incidence of the reflection beam from the second region of the wafer with respect to the determined reference position.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.